As known, for example from U.S. Pat. No. 6,323,640, rolling bearings of wheel hub assemblies of vehicles are usually equipped with a sealing assembly of the “packet” type, comprising two shields arranged side-by-side and constrained in use to a first, outer ring (usually constituting the rotating ring of the bearing in use, in this application) and a second, inner ring of the bearing (usually constituting the stationary ring of the bearing in use); the first shield integrally carries an annular seal provided with annular lips cooperating in a fluid-tight manner with the second shield in use. The bearings of this type are then also equipped with a signal generator device (also named “phonic wheel” or “encoder” in jargon) constrained to the ring rotating in use of the bearing and constituted by a further shield defined by a metallic support and by a ring made of a magnetizable plastic-based material or an elastomeric blend, magnetized so as to have an alternation of magnetized and non-magnetized zones, or having opposite polarities.
In use, the rotation of the “phonic wheel”, which as mentioned is integral with the outer ring of the bearing, allows when coupled to an appropriate sensor, to detect the rotation of the wheel of the vehicle.
However, the need to make the ring defining the phonic wheel or encoder relatively large in size to obtain a signal which can be well detected and regular at the required diameters has the drawback of creating an obstacle to the exiting of water or other contaminants which may in use overcome the second shield and come into direct contact with the outermost sealing lip of the of the annular seal.